Display screen or portion thereof with a graphical user interface



The FIGURE is a front view of a display screen or portion thereof with agraphical user interface showing the claimed design.

The outermost broken line rectangle depicts a display screen; theremaining broken lines depict portions of the graphical user interface;all broken lines form no part of the claimed design.

CLAIM The ornamental design for a display screen or portion thereof witha graphical user interface, as shown and described.